Phytochemistry and biological activity of Onosma rascheyana (Boiss.) extracts

In recent years, it has been determined that Onosma species exhibit interesting biological/pharmacological activities. The aim of this study was to analyze the chemical composition, antioxidant and enzyme inhibitory activities of the methanol (MeOH), water and ethyl acetate extracts obtained from the aerials parts of Onosma rascheyana (Boiss.). The chemical compositions of the extracts were determined using spectrophotometric and chromatographic methods. Biological activities of the extracts were determined using antioxidant and enzyme inhibitory test systems. The MeOH extract was found to be rich in both phenolics and flavonoids (31.55 mg GAEs/g and 15.20 mg REs/g, respectively). The MeOH extract also contained higher amounts of 4-hydroxybenzoic and p-coumaric acids compared to other phytochemicals. The MeOH extract exhibited remarkable activity in all antioxidant test systems. However, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS) scavenging assay resulted in superiority of water extract (88.90 mg TEs/g). The relative antioxidant capacity indices (RACI) of the extracts and the correlations between these values and antioxidant activities confirmed the high activity of the MeOH extract. In the α-amylase, α-glucosidase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity tests, the ethyl acetate extract showed high activity, while the tyrosinase inhibitory activity assay resulted in the superiority of the MeOH extract (59.72 mg KAEs/g). It was concluded that the extracts of O. rascheyana could be used as alternative agents in the food, cosmetic and medical industries due to their antioxidant and enzyme inhibitory activities